Wire-cut electrical discharge or electrical machining makes use of a continuous wire electrode of a thickness in the range between 0.05 and 0.5 mm which is axially advanced and transported from a supply side through a machining zone to a take-up side. In the machining zone there is positioned a workpiece and an EDM gap is formed between the advancing wire electrode and the workpiece. A machining fluid, typically distilled water of dielectric nature or a liquid electrolyte, is supplied to fill and flush the EDM gap while an electric current is applied between the wire electrode and the workpiece to create a succession of electrical discharges or a strong electrolytic action through the fluid medium, thereby allowing material to be removed from the workpiece. As material removal proceeds, the workpiece is displaced relative to the advancing electrode and generally transversely to the axial direction thereof along a prescribed path to form a desired cut in the workpiece.
In the path of wire travel, drive rollers driven by a motor are provided immediately upstream of the take-up side to apply a traction force to the wire to feed it at a predetermined rate of advancement. Brake rollers driven by a motor may further be provided immediately downstream of the supply side to assure that the wire travels stretched under a suitable tension along the path, which also includes a pair of guide members constituted by smooth arcuate bearing surfaces designed to change the direction of wire travel from the supply side to the machining zone and from the latter to the take-up side, respectively. These guide members may also serve as wire-positioning guides which precisely align the traveling wire in a predetermined machining position across the workpiece.
The structure of a wire-positioning guidance member therefore directly influences the machining accuracy which results.
Heretofore, two forms of the wire passage in the wire guidance and support assembly have been in use. One makes use of an internal passage formed through an elongated solid member. Such structures do not, however, allow easy mounting and dismounting of the continuous wire. In the other form, a V-shaped slot on a fixed guide body provides a bearing surface for the traveling wire but this tends to cause the traveling wire to come off, thereby giving rise to machining inaccuracy.